(CNN) -- Dropping a political bombshell, New Jersey Gov. James McGreevey announced his resignation Thursday after revealing that he is gay and that he had an adulterous affair with a man.

With his wife standing by his side, McGreevey -- a father of two -- spoke in calm tones as he described his struggle with his sexuality, "a certain sense that separated me from others." It was something that he said began as a child.

"At a point in every person's life, one has to look deeply into the mirror of one's soul and decide one's unique truth in the world, not as we may want to see it or hope to see it, but as it is," McGreevey said.

"And so, my truth is that I am a gay American," the Democrat said.

McGreevey's surprise resignation came as Golan Cipel, a former security aide to the governor, had readied a sexual harassment lawsuit against the governor, two Democratic sources told CNN. Cipel resigned his post in 2002.

A third Democratic source, who had spoken throughout the day with a top aide to the governor, told CNN it is unclear whether Cipel will proceed with the lawsuit now that McGreevey has announced his resignation.

CNN has made repeated attempts to reach Cipel for comment.

Speaking at a packed news conference in the Statehouse in Trenton, New Jersey, McGreevey admitted to an affair with a man and asked for his family's forgiveness.

"It was wrong. It was foolish. It was inexcusable," he said.

And McGreevey said he was stepping down from the state's highest office.

"Given the circumstances surrounding the affair and its likely impact upon my family and my ability to govern, I have decided the right course of action is to resign," McGreevey said.

His resignation will take effect November 15, and State Senate President Richard Codey, a fellow Democrat, will serve the the remainder of his term, which ends in January 2006.

If McGreevey's resignation had taken effect before September 15, state law would have required a special gubernatorial election on November 2.

McGreevey said his affair and sexuality -- "if kept secret" -- would leave the governor's office "vulnerable to rumors, false allegations and threats of disclosure."

McGreevey did not identify the man with whom he had the affair.

One Democratic strategist close to McGreevey said his speech was "well delivered and, I think, well received. But given what's ahead for him, it's downhill from here."

Even as he acknowledged his sexuality, McGreevey spoke of the "suffering and anguish" he had brought to his family and friends, saying he would "almost rather have this moment pass."

"For this is an intensely personal decision and not one typically for the public domain," McGreevey said of his revelation. "Yet, it cannot and should not pass."

U.S. Sen. Frank Lautenberg, a Democrat, said in a written statement that "my heart goes out to Gov. McGreevey and his family."

Democratic Chairwoman Bonnie Watson Coleman issued a written statement with a similar sentiment.

"Our hearts and prayers are with Gov. McGreevey and his family during this time," Coleman said. "The Democratic Party of New Jersey will remain strong and united as it stands behind the ideals and values that it has always fought to protect."

Garden State Equality, a gay rights group, called McGreevey's coming-out speech "poignant" and said its members' thoughts were with the governor and his family.

"We all know how difficult it is to come out as openly gay, whether to family or other loved ones," Garden State Equality chairman Steven Goldstein said. "No one could imagine what it's like to come out to 300 million people -- this is totally unprecedented."

Once considered a rising star in Democratic circles, McGreevey, 47, served in the state Legislature and as mayor of the town of Woodbridge, New Jersey, before winning the governorship.

McGreevey won the seat in 2001 by a wide margin over former Jersey City Mayor Bret Schundler and took office in January 2002.

His administration has been buffeted by some scandal.

A Quinnipiac University poll released August 4 showed McGreevey's approval among state voters fell sharply after two Democratic fund-raisers were indicted on federal charges in July -- one of them accused of lining up prostitutes to discredit a witness in a tax fraud investigation, the other accused of extortion.

McGreevey and his wife, Dina, have a 2-year-old daughter, and he has another daughter from a previous marriage.

McGreevey signed a bill in January that created same-sex domestic partnerships in New Jersey, but urged New Jersey officials to abide by current laws when the city of Asbury Park issued a marriage license to a same-sex couple in May.

In July, he condemned a proposed constitutional amendment that would limit marriage to heterosexual couples as "a divisive and drastic tactic."

Sheinkopf said the governor decided to resign after meeting with advisers and friends and even wrote his speech himself.

"It was the least scripted thing I've seen in 35 years in this business," Sheinkopf said. "What happens next is a transition that keeps things rolling forward, and keeps some of his initiatives in place."